Shielded filter

ABSTRACT

An electrical filter comprises an elongated metallic tube having a pair of open-ended cans inserted into the tube ends with the open ends of the cans being joined to the tube adjacent the tube ends. The interior regions of the tube, divided by the closed ends of the cans, contain inductance and capacitance elements electrically interconnected to one another, said interconnections including conductive tabs carried by the capacitance elements. The ends of the tube are hermetically sealed; and the interior of the tube is filled with a potting compound.

United States Patent Inventor Peter Parfitt Hove, England Appl. No.752,913 Filed Aug. 15, 1968 Patented May 18, 1971 Assignee WorcesterControls Corporation West Boylston, Mass.

SHIELDED FILTER 10 Claims, 5 Drawing Figs. I US. Cl 333/79, 333/70,333/78, 336/90, 317/256 Int. Cl H03h 7/04 Field of Search 333/70, 76,79, 78; 317/242, 261; 323/76; 336/79, 90

References Cited UNITED STATES PATENTS 2,550,244 4/1951 Gusdorf 333/787/1958 Sabaroff 333/73C 2,886,788 5/1959 Cushman 336/79 3,267,396 8/1966Scott 333/70 3,227,973 1/1966 Gray 333/78 3,191,131 6/1965 Adams 333/76Primary Examiner-Herman Karl Saalbach Assistant Examiner-C. BaraffAttorneys-William D. Hall, Elliott l. Pollock, Fred C. Philpitt, GeorgeVande Sande, Charles F. Steininger and Robert R. Pn'ddy ABSTRACT: Anelectrical filter comprises an elongated metallic tube having a pair ofopen-ended cans inserted into the tube ends with the open ends of thecans being joined to the tube adjacent the tube ends. The interiorregions of the tube, divided by the closed ends of the cans, containinductance and capacitance elements electrically interconnected to oneanother, said interconnections including conductive tabs carried by thecapacitance elements. The ends of the tube are hermetically sealed; andthe interior of the tube is filled with a potting compound.

PAIENTEDMAHBM $579,156.

PETER PARFITT INVENTOR ATTORNEY SHIELDED rrrxrsn BACKGROUND OF THEINVENTION Filters of various electrical configuration are, inthemselves, well known. Such filters may be used for low-pass, high passband-pass, band elimination, or general filtering purposes; and all ofthese various known electrical configurations are contemplated by thepresent invention.

As a practical matter, filters of the general types described comprise aplurality of electrical (inductance, capacitance and/or resistance)components interconnected in repetitive fashion to provide a successionof filter sections between cooperating input and output terminals. insuch arrangements, it is often necessary to introduce RF screening meansof some type between the various filter sections so that as a signalpasses through the filter it is not contaminated by unwantedinterference signals or trash percolating from the input end of thefilter toward its output end. Such RF screens must be of metalconstruction, and must completely isolate the filter sections from oneanother. At the present time, where it is desired to provide a shieldedfilter of the general type described, it has been normal procedure toassemble the filter components into an elongated metal tube, and, at thesame time, to place metal flanges into the tube between selected filterelements. The

metal flanges employed customarily have their edges tinned with a softsolder; and when the parts are assembled in place, a flame is passedaround the outside of the tube causing the solder to melt and adhere tothe inner wall of the tube so as to anchor the shield flanges in place.

Structures and techniques of the types described above are practicalonly when the materials constituting the overall filter are carefullyselected. The metal parts must be such that they are easily solder-ableat relatively low temperatures. Moreover the internal electricalcomponents, and'the potting materials used, must be capable ofwithstanding the temperatures required to complete the shielding joints.These requirements in turn place considerable limitations on the typesof material which can be used in any given filter, as well as upon theelectrical characteristics of the filter itself.

By way of example, it is known that a number of metals are difficult tosolder. One in particular is stainless steel. Such stainless steelmaterials require relatively high temperatures to solder, and alsoordinarily requires the use of very corrosive fluxes. When it is desiredto employ stainless steel in the filter construction, therefore, thereis considerable danger that the characteristics and. life of the filtermay be severely prejudiced by the high temperatures to which componentsare subjected during the manufacturing process, and by residual fluxremaining in the assembly after the fabrication has been completed.While the present invention is not limited to the use of stainless steelmaterials, the construction to be described does permit the use of suchmaterials without risking these disadvantages.

The known structures and techniques described are further subject to thedisadvantages that it is relatively difficult to-assemble the shieldingflanges'and components in place, it is relatively difficult to assurethat wiring interconnections between components are not disturbed orbroken during potting steps, and it is relatively difficult to eliminatepossible shifting of components and shielding elements during theoverall filter fabrication. These manufacturing difficulties arecomplicated by the fact that it is often desired to miniaturize filtersof the types contemplated herein; and such miniaturization severelyaggravates the problems already mentioned.

The present invention, by employing-a new mechanical arrangement forelectrical filters of the types described, obviates all of thesedisadvantages and permits afilter of superior electrical and mechanicalcharacteristics to be fabricated more easily, and at less cost, than hasbeen the case heretofore.

SUMMARY OF THE INVENTION In accordance with the present invention, a newfilter construction is provided wherein an elongated open-ended metallictube is fitted with a pair of opemended metallic cans insertedrespectively into the open ends of the tubes with the open can ends andopen tube ends being closely adjacent one another. Each can contains aninductance element and a capacitance element; and the interior tuberegion defined between the closed can ends contains at least one furtherfilter component (e.g. a capacitor element) or a plurality of inductorand capacitor elements. The closed can ends act as shielding elementsextending across the tube interior, so as to subdivide the tube into aplurality of sections having the desired RF isolation therebetween.

The can elements and their associated components are inserted into thetube as subassemblies, and the filter parts are then permanently fixedin place by running appropriate joints (by soldering, welding, orbrazing) between the tube and interior cans adjacent the open ends ofthe tube and cans. Due to the location of the joints thus made,corrosive fluxes may be employed, if needed, since it is possible tocompletely wash such fluxes away from the assembly before sealing theends of the tube, the joints being exterior to all electrical parts.Moreover, due to the fact that the joints are disposed closely adjacentto the open ends of the tube, itis possible to join each can to theexterior tube and to a sealing end cap in a single operation, therebyreducing the time and cost of assembly. Further, since the joints beingmade are located at the extreme ends of the cans and tubes, it ispossible to use relatively high temperatures to effect such jointswithout risking high temperature damage to the delicate electricalcomponents and the encapsulant or potting material, inasmuch as theselatter elements are surrounded by metal parts which act as a heat sinkduring the joining operation.

Further advantages are achieved by the use of inductor and capacitorelements of unique construction disposed within the aforementioned tubeand cans. The capacitors are of the extended foil type. While suchcapacitors are, in themselves well known, it has been customary practiceheretofore to attach wires to the exposed layers of foil at either endof the capacitor and to connect these wire leads to other components orto ground. The extended foil capacitors used in the present inventionare provided with conductive tags at their opposing ends, and with aninsulating sleeve extending through the capacitor between said tags.These constructional aspects of the capacitor facilitate the making ofinterconnections between components within the tube, and between thecapacitor and ground. Moreover the use of such tags provides a wide pathfor current flow, thereby reducing inductance in the capacitor; andfurther assures that slack may be removed from any wire runs betweenfilter components thereby reducing the hazard of damage to-loose wireswhen the completed filter elements are'inserted into the tube.

The inductor arrangements employed comprise turns of insulated wirewound about a toroidal core, with the overall coil then being enclosedwithin a thin skin of polywrap material shrunk about the inductance. Thecoil shape and size is related to the geometry and positioning of tagelements on the aforementioned capacitors so that the inductor andcapacitor elements can be placed in close proximity to one another, andsecurely held in desired position during completion of the overallassembly.

The overall arrangement makes it far easier to assemble the filter partsand to assure that they remain in desired positions relative to oneanother during subsequent fabrication steps; facilitates the making ofelectrical connections between the filter components; assures thatnecessary mechanical joints and hermetic sealing can be achieved withoutlimitation in the materials or joining techniques used, and withoutrisking damage to the electrical components or potting compound;

and facilitates the miniaturization of the overall filter when that isrequired.

BRIEF DESCRIPTION OF THE DRAWlNGS FIG. l is a view, in partial crosssection, of a filter constructed in accordance with one embodiment ofthe present invention;

FlG. RA is an electrical schematic diagram of the filter shown in FIG.l;

FlG. 2 is a perspective view of one form of capacitor employed in thefilter of HG. l;

FIG. 3 is a perspective view of another form of capacitor used in thefilter of FIG. l; and

FIG. 4 is detail view of an alternative filter end cap construction inaccordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG 1 shows a filterconstructed in accordance with the present invention. The filterincludes a casing comprising a tube ill) which may be fabricated of anyappropriate material, e.g., mild steel, stainless steel, aluminum,brass, etc. Casing tube it) is of elongated hollow configuration (ofcircular or other desired cross section) and includes a pair of openends 11 and 12 which are subsequently closed by end caps l3 and M, to bedescribed.

Tube ll encloses a filter assembly (which is normally preassembled andthen inserted into said tube) comprising, inter alia, a pair of cans 15and 16 respectively having open ends 15a, lot: and closed bottom walls1511, T61). Cans l and 16 are sopositioned relative to one another intube that the open ends 1511 and lba of the cans are disposed closelyadjacent to the ends lll and R2 of tube 10, with bottom walls i512 and16b of said cans being positioned inwardly in spaced relation to oneanother and to the ends ill and 12 of tube 110. Cans l5 and 16 sliclablyfit the interior of tube lit) (as will be described) and, when said cansare in place, good electrical contact is effected between the cans andtube by solder joints therebetween located closely adjacent the oppositeends of the tube It). in normal practice, tube 10 is grounded, wherebycans l5 and lo are similarly at ground potential. The bottom walls 115!)and lob of the cans are similarly at ground potential and extend acrossthe interior of the tube so as to subdivide the tube into three regionsgenerally designated l7, l8 and 19 which regions are, for all practicalpurposes, shielded from one another by the intervening grounded wallsl5!) and lob.

Filter section l7, comprising the interior of can l5, contains acapacitor 20 and an inductor 21. Capacitor 20 (and, for that matter, theother capacitors to be described hereinafter) is of the the extendedfoil type and comprises a first plurality of aluminum foil layers 22separated by appropriate insulation strips (not shown) from a furtherplurality of aluminum foil layers 23. The several foil layers 22 areinterconnected to one another by means of an elongated flat tag 24soldered to one end of capacitor 20. Tag 24 is provided with end flanges25 (see FIGS. IA and 2) shaped to conform to the interior of can l5 andeventually soldered thereto by means of solder joints 26. Thismechanical arrangement of parts comprising capacitor 20 insures that thecapacitor is accurately positioned, and maintained in position, withintube to and can 15, and further assures that, electrically, the severalfoil layers 22 are at ground potential. The side of capacitor 20,comprising foil layers 22 connected to tag 24, are, by the arrangementdescribed, grounded in a plane extending across the interior of thefilter in spaced relation to the additional ground plane supplied bybottom wall b of can 15.

The several foil layers 23, comprising the other side of capacitor 20,are interconnected to one another by a wire 27 extending across andsoldered to the exposed foil ends of layer 23. An elongated sleeve 28 ofinsulating material extends along the axis'of the capacitor with one endprotruding through solder tag 24, and wire leads 31 (from inductor 21)and 27 pass axially through the capacitor via sleeve 23. Leads 27 and 31are soldered, as at 30, to wire lead 29 which extends to terminal 53. ofthe adjacent end cap 13. By this arrangement of leads, lead 31 can bepulled tight after the inductor and capacitor elements have beenassembled into can l5.

Inductor 21, which is also located within can 15 in filter region 17,comprises a toroidal core having insulated wire wound thereon, with theresultant inductor being enclosed within a thin skin of polywrapinsulating material, having a thickness of, for example, 0,004 inches,shrunk around the outer diameter of the inductor. This insulating skinneed not cover the inductance wires completely. Inductor 21 is providedwith a pair of elongated flying leads 31 and 32 a portion of which maybe tinned to facilitate the making of electrical connections. Lead 3iis, as previously described, soldered at point 30 to provide electricalcontinuity between lead 29, one side of capacitor 20, and one end ofinductor 21 (see FIG. 11A).

It will be noted that the body of capacitor 20 is positioned offcenterrelative to the axis of tube 10 and relative to the center line ofinductor 21. This assures that the body of capacitor 20 does not sealoff the area around the axis of inductor 21, whereby encapsulant cancompletely fill all spaced around capacitor 20 and inductor 2i. Theoffcenter configuration of capacitor 20 further ensures that the liveend of capacitor 20 contacts the insulation material surroundinginductor 21.

The central section 18 of the filter comprises a pair of capacitors 35and 36 and a further inductor 37 physically positioned therebetween.Froman electrical point of view each of the capacitors 35 and as issimilar to that already described in reference to capacitor 20, i.e.capacitors 35 and 36 each comprise alternate layers of aluminum foilseparated from one another by appropriate insulation strips. A firstplurality of the foil layers in capacitor 35 have their exposed endssoldered to an elongated relatively wide wide tag 38 (see FIG. 3), andsolder tag 38 is in turn soldered to the outer surface of bottom wall15b of can 115. As a result, one side of capacitor 35 is grounded (seeFIG. 1A).

The second plurality of foil layers in capacitor 35, compris ing theother side of the capacitor, have their exposed end interconnected to afurther tag 39 soldered thereto. Tag 39 has opposing, inwardly inclinedflanges 12 which are shaped to engage one side of inductor 37. Tag 39and its associated flanges d2 further provide two soldering points 43and 44 for wiring, to be described.

A central insulating sleeve 4a extends along the axis of capacitor 35,with the opposing ends of sleeve 40 protruding through the tags 38 and39. Bottom wall 15b of can 15 is provided with a central aperture 41adapted to receive a protruding end of insulation sleeve 40 when tag 38is properly positioned in place for attachment to said bottom wall 15b.

As a result of the arrangement described, lead 32 may be passed frominductor 2i through insulating sleeve 40 for electrical connection withthe live side of capacitor 35 at solder point 43; and further connectionmay be made between said live side of capacitor 35 and one end ofinductor 37 by means of lead 45.

Capacitor 36 has a physical and electrical configuration entirelysimilar to that already described in reference to capacitor 35. To thiseffect, one side of capacitor 36 is provided with a tag 416 soldered tothe exposed foil layers at one end of said capacitor, and provided withinwardly extending flanges 87 engaging inductor 37. Flanges 42 and 47thus accurately position, and maintain in position therebetween,inductor 37. Flanges 47 provide solder points (similar to points 43 and44) for leads extending between inductor 37 and capacitor 36. The otherend of capacitor 36 has a further tag 48 (like tag 38) soldered to theexposed foil layers and also soldered to the grounded bottom wall lob ofcan 16.

The third filter region 19 comprises an inductor 49 associated with acapacitor 50. Elements 49 and 50 are arranged, both mechanically andelectrically, in the manner already described with refere n :e toelements 21 and 20, and no further description of these elements istherefore necessary.

The several filter components described are assembled in stages assubassemblies, and then inserted into tube 116. The first subassemblycomprises can 15 with capacitor 20 and inductor 21 mounted in place, andwith capacitor 35 affixed to the exterior of bottom wall 15b. The secondsubassembly comprises can 16 with components 49 and 50 therein, and withcomponents 36 and 37 attached to the exterior of can 16. The can 16subassembly is slidably inserted into one end of tube (the right-handend as viewed in FIG. 1) and then pushed into the interior of tube 10until bottom wall 16b of the can 16 subassembly engages a locationdimple 10a protruding inwardly from tube 10. At this time, inductor 37will be located closely adjacent the left-hand end of tube 10, as viewedin FIG. 1. Electrical connection 44 in then made between inductor 37 andthe can subassembly which, at this time, is outside of tube 10. The can15 subassembly is then inserted into the lefthand end of tube 10 inengagement with inductor 37, and is slidably pushed into tube 10 to pushthe can 16 subassembly back down tube 10 toward the right-hand endthereof until bottom wall 15b of can 15 engages location dimple 10a. Bythis series of manipulative steps, all of the components shown in FIG. 1(other than the end caps) are properly positioned relative to oneanother within tube 10, and are properly connected electrically to oneanother.

Once the several filter components are interconnected in the mannerdescribed, the overall assembly may be encapsulated in an appropriatepotting compound. Encapsulation takes place while the assembly is intube 10. In a first stage, potting compound is introduced into theright-hand end of tube 10 so as to fill the interior of can 16; and thisfirst mass of potting compound is then cured. The complete assembly isthen moved to the left (as viewed in FIG. 1) so as to push the can 15subassembly out of tube 10 until central filter section 18 is open; andpotting compound is then inserted into the center section in surroundingrelation to the elements 35, 36, and 37. The can 15 subassembly is thenpushed back into place in tube 10 with can 15 acting as a piston; andfurther potting compound is thereafter inserted into can 15. The massesof potting compound in can 15, and in center filter section 18, are thencured at the same time.

It will be appreciated that, in the alternative, encapsulation may beeffected by providing one or more apertures in the sidewalls of tube 10adjacent filter section 18 so that potting compound may be introducedinto the ends and interior of tube 10 while the filter parts are inplace. Such apertures, if provided, can thereafter be closed by solderor the like.

After the several components are assembled and encapsulated, theopposing ends of the overall filter structure may be electricallyconnected to terminals 51 and 52 in end caps 13 and 14, whereafter saidend caps may be hermetically sealed in place across the opposite ends oftube 10. Central terminals 51 and 52 are mounted in, and extend through,ceramic por tions of the end caps acting to insulate said terminals frommetallic end cap annuli 53 and 54. Annuli 53 and 54 are shaped toconform to the interior of tube 10, and engage the open ends of cans 15and 16 as illustrated. When the end caps are in place, a mechanical andhermetic seal may be achieved by means of solder, as at 55 and 56.Solder joints may, at the same time, also be made between tube 10 andcans 15 and 16 at positions closely adjacent the open ends of said cansto assure good ground connections between the tube and cans.

The overall structure thus described has a number of significantassembly and mechanical advantages, some of which have already beendiscussed. The overall filter, including shield planes 15b and 16b maybe held in place within, and electrically connected to, tube 10 by meansof solder joints located closely adjacent the open ends of tube 10 inrelatively widely spaced relation to said ground planes and to theelectrical filter components. These joints may, moreover, be made at thesame time that the end caps are sealed in place thereby simplifyingoverall fabrication of the assembly. Other joining techniques may beemployed to similar advantage, including brazing and welding, dependingupon the particular materials employed for the filter parts. In anyevent, the joints between the filter assembly and tube 10 are located insuch position relative to the metal parts of the structure that themetal parts of the structure act as a heat sink, thereby preventingelectrical components and encapsulant from being subjected to excessiveheat during any joint-making steps.

The tag constructions employed of on the several capacitors facilitatethe making of interconnections between the filter components, assurethat the parts are accurately positioned and maintained in positionduring assembly and thereafter, and minimize possible damage to wiresduring the assembly and encapsulation steps. In this latter respect, itwill be noted that solder points such as 43 and 44 are positioned on theoutside diameter of a capacitor such as 35 or 36 whereby, prior tosoldering, the components to be joined can be drawn tightly together soas to remove slack from the wires and reduce the hazard of damaging aloose wire when the completed filter elements are inserted into tube 10.

The use of insulated sleeves extending through the center of eachcapacitor facilitates the passing of wires between adjacent components,and again makes it possible to removed slack from the wires so as toeliminate the hazard described above. Moreover, the insulating sleeve ineach capacitor assists in bringing each filter soldering joint (e.g. 30)into an easily accessible position, which greatly facilitatesminiaturization of the filter.

The use of metal 'cans constructed and arranged in the manner describedassures that RF shield or screen planes may be disposed between sectionsof the filter in a far easier manner than has been possible heretofore.One or more such cans may be employed in a given tube, depending uponthe number of filter sections to be provided. The use of such cansenables the sealing joints to'be made at the exterior parts of theassembly, and, as previously described, permits the use of corrosiveflux (when needed) during the joint making steps without risking damageto the filter or its component parts.

Various modifications may be made to the filter arrangement describedwithout departing from the present invention. By way of example, filtersection 18 in the arrangement of FIG. 1 is illustrated as comprising twocapacitors and an inductor. However, it will be appreciated that filtersection 18 may comprise only a single capacitor. Indeed, it will furtherbe appreciated that the electrical nature of the components which areplaced in the several filter sections, and the number of filter sectionswhich are employed, may be varied as necessary to achieve a'filterhaving any desired electrical characteristics.

It will further be appreciated that the soldered end cap constructionshown in FIG. 1 is not mandatory. FIG. 4 shows an alternativeconstruction wherein a tube such as 10 and a can such as 16 areassociated with an end cap 60 provided with a metal annulus 61 which iswelded in place along joints 62. This welding technique simultaneouslysecures the end cap in place and physically joins can 16 to tube 10.

Still further arrangements will be suggested to those skilled in theart. It must therefore be understood that the foregoing description isintended to be illustrative only and not limitative of my invention; andall such variations and modifications as are in accord with theprinciples described are meant to fall within the scope of the appendedclaims.

lclaim:

1. An electrical filter comprising an elongated hollow tube ofconductive material, a can member of conductive material, said canmember comprising a bottom wall integral with transversely extendingcontinuous sidewalls, said sidewalls defining a free edge relativelywidely spaced form said bottom wall,

said can member being disposed within said elongated tube with itsbottom wall positioned transverse to the axis of said tube and extendingcompletely across said tube at a location between and relatively widelyspaced from both opposing ends of said tube, the integral sidewalls ofsaid can member being located closely adjacent to and extending alongthe interior surface of said tube with the free edge of said sidewallsbeing positioned closely adjacent one of the opposing ends of said tubeat a position remote from said bottom wall location, first electricalfilter components located within said can member between said bottomwall and said one end of said tube, second electrical filter componentslocated outsideof said can member but within said tube between saidbottom wall and the other end of said tube, whereby said bottom wallacts as a shield between said first and second electrical filtercomponents, and means for closing said one end of said tube at a jointlocated closely adjacent the free edge of said can sidewalls.

2. The structure of claim 1 including means in said tube for fixing thelocation of said bottom wall relative to the opposing ends of said tube.

3. An electrical filter comprising an elongated hollow tube ofconductive material, a first can member comprising a bottom wallintegral with upstanding sidewalls defining an open top spaced from saidbottom wall; said first can member being disposed within said elongatedtube with its bottom wall positioned transverse to the axis of said tubeat a location between the opposing ends of said tube, the sidewalls ofsaid first can member being located closely adjacent the interiorsurface of said tube with the open top of said first can member beingpositioned closely adjacent one of the opposing ends of said tube, asecond can member having a bottom wall, integral sidewalls, and an opentop, said second can member being disposed within said tube with itsopen top positioned closely adjacent the other end of said tube and withits bottom wall positioned transverse to the axis of said tube at alocation axially spaced from the bottom wall of said firstcan member,first electrical filter components located within said first can memberbetween its bottom wall and said one end of said tube, second electricalfilter components located within said second can member between itsbottom wall and the other end of said tube, further electrical filtercomponents located within said tube between the spaced bottom walls ofsaid first and second can members, and closure means closing theopposing ends of said tube.

4. The structure of claim 3 wherein each of said bottom walls includesan aperture, and electrical means extending through said apertures forinterconnecting said first, second, and further electrical filtercomponents to one another.

5. The structure of claim 3 wherein said first electrical filtercomponents include a capacitor, a conductive strap electricallyconnected to one side of said capacitor, said strap extending at leastpartially across said first can member in a direction generallyparallel-to its bottom wall and conductively engaging the sidewalls ofsaid first can member.

6. The structure of claim 5 wherein said capacitor includes a sleeve ofinsulating material extending therethrough, and an electrical leadconnected to one side of said capacitor and extending through saidsleeve for electrical connection to a filter component physicallylocated adjacent the other side of said capacitor.

7. The structure of claim 3 wherein said further electrical filtercomponent include a capacitor, a conductive strap electrically connectedto one side of said capacitor, said strap extending at least partiallyacross said tube in a direction transverse to the axis of said tube andconductively engaging the bottom wall of a can member.

8. An electrical filter comprising an elongated hollow tube ofconductive material, a can member comprising a bottom wall integral withupstanding sidewalls defining an open top spaced from said bottom wall,said can member being disposed within said elongated tube with itsbottom wall positioned transverse to the axis of said tube at a locationbetween the opposing ends of said tube, the sidewalls of said can memberbeing located closely adjacent the interior surface of said tube withthe open top of said can member being positioned closely adjacent one ofthe opposing ends of said tube, first electrical filter componentslocated within said can member between said bottom wall and said one endof said tube, second electrical filter components located within saidtube between said bottom wall and the other end of said tube, andclosure means closing the opposing ends of said tube, said filter comnents includin a capacitor of the extended foil type, an e ongatedconduc we strap attached to one side of said capacitor, said strapincluding positioning flanges at its opposing ends, and an inductorphysically engaging said positioning flanges.

9. The structure of claim 3 wherein said closure means comprises endcaps hermetically sealing the opposing ends of said tube, said end capsincluding terminals electrically connected to said filter components.

10. The structure of claim 3 wherein said tube and said can members areeach of circular cross section.

1. An electrical filter comprising an elongated hollow tube ofconductive material, a can member of conductive material, said canmember comprising a bottom wall integral with transversely extendingcontinuous sidewalls, said sidewalls defining a free edge relativelywidely spaced form said bottom wall, said can member being disposedwithin said elongated tube with its bottom wall positioned transverse tothe axis of said tube and extending completely across said tube at alocation between and relatively widely spaced from both opposing ends ofsaid tube, the integral sidewalls of said can member being locatedclosely adjacent to and extending along the interior surface of saidtube with the free edge of said sidewalls being positioned closelyadjacent one of the opposing ends of said tube at a position remote fromsaid bottom wall location, first electrical filter components locatedwithin said can member between said bottom wall and said one end of saidtube, second electrical filter components located outside of said canmember but within said tube between said bottom wall and the other endof said tube, whereby said bottom wall acts as a shield between saidfirst and second electrical filter components, and means for closingsaid one end of said tube at a joint located closely adjacent the freeedge of said can sidewalls.
 2. The structure of claim 1 including meansin said tube for fixing the location of said bottom wall relative to theopposing ends of said tube.
 3. An electrical filter comprising anelongated hollow tube of conductive material, a first can membercomprising a bottom wall integral with upstanding sidewalls defining anopen top spaced from said bottom wall, said first can member beingdisposed within said elongated tube with its bottom wall positionedtransverse to the axis of said tube at a location between the opposingends of said tube, the sidewalls of said first can member being locatedclosely adjacent the interior surface of said tube with the open top ofsaid first can member being positioned closely adjacent one of theopposing ends of said tube, a second can member having a bottom wall,integral sidewalls, and an open top, said second can member beingdisposed within said tube with its open top positioned closeLy adjacentthe other end of said tube and with its bottom wall positionedtransverse to the axis of said tube at a location axially spaced fromthe bottom wall of said first can member, first electrical filtercomponents located within said first can member between its bottom walland said one end of said tube, second electrical filter componentslocated within said second can member between its bottom wall and theother end of said tube, further electrical filter components locatedwithin said tube between the spaced bottom walls of said first andsecond can members, and closure means closing the opposing ends of saidtube.
 4. The structure of claim 3 wherein each of said bottom wallsincludes an aperture, and electrical means extending through saidapertures for interconnecting said first, second, and further electricalfilter components to one another.
 5. The structure of claim 3 whereinsaid first electrical filter components include a capacitor, aconductive strap electrically connected to one side of said capacitor,said strap extending at least partially across said first can member ina direction generally parallel to its bottom wall and conductivelyengaging the sidewalls of said first can member.
 6. The structure ofclaim 5 wherein said capacitor includes a sleeve of insulating materialextending therethrough, and an electrical lead connected to one side ofsaid capacitor and extending through said sleeve for electricalconnection to a filter component physically located adjacent the otherside of said capacitor.
 7. The structure of claim 3 wherein said furtherelectrical filter component include a capacitor, a conductive strapelectrically connected to one side of said capacitor, said strapextending at least partially across said tube in a direction transverseto the axis of said tube and conductively engaging the bottom wall of acan member.
 8. An electrical filter comprising an elongated hollow tubeof conductive material, a can member comprising a bottom wall integralwith upstanding sidewalls defining an open top spaced from said bottomwall, said can member being disposed within said elongated tube with itsbottom wall positioned transverse to the axis of said tube at a locationbetween the opposing ends of said tube, the sidewalls of said can memberbeing located closely adjacent the interior surface of said tube withthe open top of said can member being positioned closely adjacent one ofthe opposing ends of said tube, first electrical filter componentslocated within said can member between said bottom wall and said one endof said tube, second electrical filter components located within saidtube between said bottom wall and the other end of said tube, andclosure means closing the opposing ends of said tube, said filtercomponents including a capacitor of the extended foil type, an elongatedconductive strap attached to one side of said capacitor, said strapincluding positioning flanges at its opposing ends, and an inductorphysically engaging said positioning flanges.
 9. The structure of claim3 wherein said closure means comprises end caps hermetically sealing theopposing ends of said tube, said end caps including terminalselectrically connected to said filter components.
 10. The structure ofclaim 3 wherein said tube and said can members are each of circularcross section.